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Tube Amp - Headroom, Wattage, Cab Choice


butcherNburn

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I have an Old Ampeg B-25, all tube, 55 Watt Head.

(that explains why I'm distorted and walk funny)

In the near future, I'll be shopping around for a cab, but I have some concerns.

 

I love this Amp and have played it through a few cabs with varying success. Usually if the speaker is decent, the sound is decent. The 10" attached to my carvin combo is OK and my old "Frankenstein" 15" wasn't bad either. The beat-up, Peavy cabs at a rented rehearsal studio, sounded horrible, but I think they would have sounded bad no matter what amp was used. I tried a few others with similar results.

 

Now this Amp is 55 "all tube" watts which, as you know, can sound significantly louder. It originally came with a 2x15" cab.

I really learned a lot on previous threads regarding the Amp wattage to Cab rating and headroom / clipping factors. But what I would like to know is:

Should I specifically look for a lower wattage cab to compensate for this amp?

or

Should I treat this like a higher wattage head, due to it's apparent power?

and

Would my quality of sound suffer with the wrong "good quality" cab?

 

What I'm looking for is the best possible sound, not necessarily higher volume. Enough to keep up with drums and a "reasonably easy tricked (volume knob) guitarist" at practice levels. I plan on using it for some miked recording as well. Due to the heavy weight and fagility of this amp, it won't be traveling. What I'm thinking of right now is either a 2x12" or single 15", used.

 

Part of my problem is, once again, due to the heavy weight and fagility of this amp, bringing it from shop to shop to try cabs, may be out of the question. I don't think they would appreciate me hooking up the old girl to their new cabs either.

 

Before I buy anything I do solemnly swear to 1 hour of good solid (not weak) practice for each dollar I spend on the cab.

 

I know I'm rambling but I'm anxious about having my own dedicated music room soon and taking this baby out of storage.

If you think my playing is bad, you should hear me sing!
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Watts are watts. 55 watts tube = 55 watts solid state.

 

Are you playing with sound reinforcment? If so, just make sure the cabinet it loud enough for stage volume.

 

There are two options:

 

1. Get a REALLY efficient cabinet. Think folded horn...

 

2. Get a power amp and a cabinet. Feed the power amp with the signal from the tube amp and drive the cabinet with the power amp.

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I disagree with my good friend, Getz76.

 

Tube watts always sound louder than solid state watts.

 

It doesn't matter if the cabinet is rated for 55 watts or 550 watts if you are using this amp.

 

The only kind of cab you don't want to get is one that is "power hungry", one that requires a lot of watts to sound loud. A lot of modern cabinets trade efficiency for volume.

 

If I were you, I'd be looking for a used Boogie 15".

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I'd have to disagree with you too Getz.

 

A tube 100 watt Peavey 5150 2x12 combo on less-than-1 sounded louder than a solid state 100 watt Line-6 2x12 on 5.

 

definitely a difference between tube watts and SS watts.

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You're comparing apples and oranges. Different preamps and different cabinets.

 

I'll continue to contend...

 

Take the same preamps and put through a solid-state poweramp and a tube poweramp.

 

It is true that a overdriven tube power section tends to sound better than a solid-state power section being overdriven (again, this is a generalization), so yes, you can infer that a tube power section sounds "louder" because you're driving it harder.

 

However, don't expect to drive an SWR Megolith with this amp.

 

Again, shy away from newer cabinets. As Jeremy said, newer cabinets are designed with different intentions; they give up on efficiency for weight, size, and response.

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Originally posted by   :

The only truisms about quote tube watts unquote are:

 

(1) THEY WEIGH MORE.

(2) THEY COST MORE.

(1) It weighs about 65 Lbs.

(2) I actually only paid $50 for it. With shipping, it was just over a dollar a pound. I wish you could buy basses that way.

Since I heard that most of the tubes were hard to find, I priced out a complete replacement once... $250 ouch!

If you think my playing is bad, you should hear me sing!
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Originally posted by   :

The only truisms about quote tube watts unquote are:

 

(1) THEY WEIGH MORE.

(2) THEY COST MORE.

So why did my SVT sound so much louder than my GK 800rb? Was I imagining it? Because it was black? I've heard theories. I guess I'm still unclear.
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You could get a 4000 watt solid-state amp that weighs 55 pounds.

 

I'll rephrase my earlier statement.

Tube watts sound louder to me because you can turn them up to their maximum and the distortion is musically pleasing...you can't do that with solid state. There is also something about which frequencies get emphasized which my pseudo-science knowledge cannot explain, but it's been talked about on-line ad nauseum.

 

And of course one watt equals one watt and I don't currently own any tube amps because of that.

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So why did my SVT sound so much louder than my GK 800rb?
Because the GK was falsely rated? Because it had a way different gain structure so that 5 on its knobs wasn't the same as 5 on the SVT knobs? Because the GK didn't have a decent overdrive or distortion?

 

If you add overtones (even subtle tube overdrive does) in just enough amount for the ear to detect them, it seems a little more present even if it won't add any movement to any metering that is monitoring the process. This is also what goes on with exciters. They synthesize or through distortion/shifting of phase add upper partials.

 

There are lots of factors. Tube power sections are not linear like so called solid state are; ie a 10 dB difference in input may only make a 3 dB difference in ouptut. The manufacturers set them up so at lower master volume settings they are already pretty damn loud. But when they hit the ceiling - their potential - they simply act like compressors.

 

If tube amps were unequivocally louder they would be used for high power sound reinforcement for touring where money is no object (to the "record" comnpanies anyway, since the artists pay for it without often having a clue). But they aren't.

 

I think I've posted on this topic in detail a number of times, and told SS players how to have the best of both worlds.

.
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Although I or anyone else haven't mentioned amp types, Class A - B - C, etc. in the "tube world" also plays a factor. Anyone that has stood next to a Class A Vox 30 watt can attest to that. What I was talking about was "apparent volume" aka "what it seems like". Kind of like, if a guitarist is playing through a full stack 100 watt Marshall, it seems that is only as loud as a 500 watt bass stack, for varying reasons which have been made clearly in previous posts (and topics).

 

I am thankful that, we as bassists, are not of the "mindless masses" that only tubes are good. We have and open mind, and a significantly different instrument and sound to reproduce that solid state can provide, in spades.

 

Thanks for the advice so far people. It's just a classic head, with a unique sound I was referring to... I was looking for an answer regarding headroom when really, you pointed me in the right direction (I hope) of efficiency.

If you think my playing is bad, you should hear me sing!
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Take an all-tube head. It's got two major sections: the preamp, and the power stage (tube power amp).

 

The preamp is easy enough to deal with. Just get a tube preamp (even one tube will sound "tubey" if the design fully uses it) or a preamp with a tube emulation circuit. Either apporach will definitely give you the start of a good clean tone, and maybe take you as far as the typical dirty SVT sound.

 

So that part is easy enough to do. Coupled with a solid state amp, you will have an increased "glassy" presence that comes from accentuated harmonics and nonlinearity at the preamp stage, due to the compressed nature of tube input gain structures. Actually some of the tube emulation these days is like an idealized tube. Sansamp and Peavey (Transtube) and Carvin all do well...

 

The part most people neglect is the power stage. In tube amps this section provides a lot more non-linearity yet, and overtones exaggerated. As you hit it harder it begins to squish the dynamics and it is not unlike a compressor in that the frequency balance gets a little skewed. Actually (here comes a big generality mostly predicated on older tube designs such as the Bassman) a tube power stage seems a bit mushy when you ask it to do more bass and lower freq's - especially noticable on the lower-pitched strings.

 

A tube power stage tends to be underdamped as you go lower - often called "overhang", the sound is not as tight and focused. And low notes because of their big energy often push it into breakup earlier so the definition one desires may not be entirely there. This might be a big reason bassists have favored solid state or hybrid (tube pre, SS amp) sounds.

 

But there still can be an apparent volume difference between the all-tube rig and the hybrid one, for clean sounds especially... I've mentioned compression repeatedly, which should give you a clue at how to go about getting that. That's righ: use a compressor after the preamp and just before the power amp. If you want to still retain the best punch a GOOD compressor - possibly dual or multi band - is the way to go. Another possibility is the Aphex C2 or whatever with Big Bottom. I found it to be a little uneven in that it gave more apparent presence and sustain to the higher-pitched strings than to the lowest but it can sound pretty damn glassy-clean and decidely non-linear for the first few overtones, and the exciter portion can add a little emphasis to the rest of the sound. But I think the Rane DC24 multiband compressor does a better job. It's easier to have even-ness for the entire range of the instrument and to keep all the sense of dynamics that SS is good at, while still getting a higher average output.

 

Note here that any power amp with a built-in limiter can also provide at least a good 3 dB higher average volume if driven sufficiently.

 

Finally, some people want more grunge. So there are a lot of pedals one can run in front of the preamp if that is the case. Then you can do cascading and ultragain sounds from severed overdrive to all-out distortion and fuzz.

 

Summary: if you think you are getting less apparent volume with an SS rig, there are several ways to get MORE - without sacrificing clean tone, bass tightness and punch that all-tube rigs typically are less good at. You can also heap on the distortion if that's what you want.

.
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butcherNburn: {...} What I was talking about was "apparent volume" aka "what it seems like". Kind of like, if a guitarist is playing through a full stack 100 watt Marshall, it seems that is only as loud as a 500 watt bass stack, for varying reasons which have been made clearly in previous posts (and topics).
Actually, tubes have only a little to do with that. The thing is the gutarist is typically an octave above, and that alone means MASKING comes into play. He masks your tone. Add distortion and he REALLY masks your tone. This is an acoustci phenomena that cannot be evaded, and lower pitched instruments get masked by higher pitched ones unless the higher pitched ones unless they are closer to sine wave tonality.

 

The other thing is that bass speakers are less efficient. That is a tradeoff that typically means that to get 100 decibels the bassist is going to need more speakers and almost certainly way more power. We could be talking a difference of 6 to 10 decibels here, which is the equivalent of at least FOUR times as much power needed by the bass (without worrying about masking).

 

Then there is the human ear. It simply is a crapload less efficient at hearing frequencies below 125 Hz. And at lower volumes it gets considerably worse at it. Look on the wwweb for a graph of the Fletcher-Munson curve to see how much an advantage the guitar has here. The ear has its highest efficencies in the upper midrange and the lower treble region. This is where electric guitar lives, and where el gtr SPEAKERS are at their most efficient.

 

I am thankful that, we as bassists, are not of the "mindless masses" that only tubes are good. We have and open mind, and a significantly different instrument and sound to reproduce that solid state can provide, in spades.
Well, bassists as a tribe chose SS for portability and less maintenance cost one couls suppose. But also, once bassists heard it was possible, I think bassists wanted a clean tone that could be heard, with more punch. But the grindy sounds of yesteryear, and the warm subtle overdrives, still are great to have around. Ampeg still excels at this.

 

But now its possible to have it all.

.
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I was just going to drag up an old post or two which I talked of this. But the SEARCH at MusicPlayer.com still seems broken when using Registered Member Number and more than one keyword (sometimes even with just one keyword).

 

Thanks for the THANKS! : }

.
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Great info " "! I think you've covered everything and more succinctly and accurately than I would have managed! ;)

 

As I've been getting to know my pedals better I've really got into my Fulltone Bassdrive's different facets, from fullbore almost fuzz, down through various overdrives to fairly convincing tube amp simulation. And the extra loudness without using any more power that these settings give is quite amazing - it lets the Acmes comfortably drown out everything! :D

 

Alex

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To be honest, I could have tightened it up a little and presented a little more in-depth scrutiny too. But I think there's enough there to really think about and put into practice and experiment with, for those who want to take tone and volume farther without just buying equipment nilly-willy.
.
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BnB said something about Class A, B, C, D, etc amps.

 

What is the difference between the classes?

 

I'm a tad confused.

 

Maybe you can clear this up Anonymous Man.

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Originally posted by C.Alexander Claber:

Great info " "! I think you've covered everything and more succinctly and accurately than I would have managed! ;)

Seconded. Thanks to you I can justify keeping my old 80s SVT head and coming up with the $250+ every other year for the tube replacement/bias work.

:thu:

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Thanks to you I can justify keeping my old 80s SVT head and coming up with the $250+ every other year for the tube replacement/bias work.

:thu:

You don't need me to do that. If I had one left over from back when I'd probably keep it too. Well, maybe not. I went through tubes for a number of years for my sax rig and it was expensive and it seemed like the noise floor went way down when I went to SR power amps.
.
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BnB said something about Class A, B, C, D, etc amps. What is the difference between the classes? I'm a tad confused. Maybe you can clear this up Anonymous Man.
Yes, I can clear that up. use your current search engine and type in the keywords google toolbar. Then follow the trail and install google toolbar. Then, into the google stringgadget, type in the keywords "power amp class". You will find a cornocopia of information on the subject that my modest skills could not possibly encapsulate so well.

 

Or you could use SEARCH here; I think I've seen a couple explanations go by from robb and others, possibly even me. When I wasn't so modest. Ahem.

.
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Well, I find this misleading. A solid state watt is not a tube watt when it comes to music. Tube power amps have a jumpin' out at ya quality that solid state power amps simply do not have. Some of the really fine stuff like Meyer begins to take on a little bit of that. A little bit. And that's when very carefully designed with the speakers as a whole system.

 

There are some things to be said for solid state bass amps, for sure- but they never sound anywhere as much like acoustic instruments as a tube bass amp can. There's that 3D effect. There's a sense of connecting physically there that takes place a whole lot quieter than it ever does with solid state.

 

The fact is, if the big touring sound companies were dedicated to getting the best possible sound at any expense and effort, they would be using tube rigs. Most of that sound really sucks. It's louder than hell, but it doesn't sound good. It's rarely musical. But doing it really beautifully is a pretty tall order indeed. And you can blare harsh phase-cancelled mush at most folks and they are vaguely impressed with the sheer scale of the thing, and all the hype and bs. It's not about fine sound.

 

I would say for the original poster, get an Ampeg V4B, vintage, if you can find one in primo shape or if you have a first rate tech to put it back into shape. It's rated at 100 watts per channel which is only twice what the B-25 is rated at, but it acts a lot differently. And it's a lot less heavy than an SVT and cheaper to retube. BTW, if your biases are set right, and you use standby like you should (1 minute warmup before turning on the sound, 1 minute cooldown after, don't move the amp while the tubes are hot if you can help it), retubing shouldn't be something that happens very often at all.

A WOP BOP A LU BOP, A LOP BAM BOOM!

 

"There is nothing I regret so much as my good behavior. What demon possessed me that I behaved so well?" -Henry David Thoreau

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Originally posted by butcherNburn:

But what I would like to know is:

Should I specifically look for a lower wattage cab to compensate for this amp?

or

Should I treat this like a higher wattage head, due to its apparent power?

and

Would my quality of sound suffer with the wrong "good quality" cab?

 

What I'm looking for is the best possible sound, not necessarily higher volume. Enough to keep up with drums and a "reasonably easy tricked (volume knob) guitarist" at practice levels. I plan on using it for some miked recording as well. Due to the heavy weight and fragility of this amp, it won't be traveling. What I'm thinking of right now is either a 2x12" or single 15", used.

 

Part of my problem is, once again, due to the heavy weight and fragility of this amp, bringing it from shop to shop to try cabs, may be out of the question. I don't think they would appreciate me hooking up the old girl to their new cabs either.

Ok this post went off in a completely different direction than I had intended.

 

Originally posted by getz76:

1. Get a REALLY efficient cabinet. Think folded horn...

Originally posted by jeremyc:

It doesn't matter if the cabinet is rated for 55 watts or 550 watts if you are using this amp.

The only kind of cab you don't want to get is one that is "power hungry", one that requires a lot of watts to sound loud. A lot of modern cabinets trade efficiency for volume.

 

If I were you, I'd be looking for a used Boogie 15".

Thanks!

 

What did throw me about cab choices was the Amps 55 watt rating and the fact that it was originally partnered with a 2x15". I'm off to first figure out the definition of an "efficient" speaker, and the twilight zone of accurate manufacturer published ratings (yes the "search funk-shun" will be my first recourse). Thanks to all that replied I value all your replies and most of your opinions.

If you think my playing is bad, you should hear me sing!
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The trouble with efficient speaker cabinets is that they are usually very large, and hence even less fun to tote than the SVT. There may be relative exceptions- I wonder what?

A WOP BOP A LU BOP, A LOP BAM BOOM!

 

"There is nothing I regret so much as my good behavior. What demon possessed me that I behaved so well?" -Henry David Thoreau

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I've fooled sooooo many audiophiles just by diversion... One guy was

hooked on a particular XXX model 15" cab. I had one with the speaker

removed for repair, so I just put INSIDE the cab a small full range

steel speaker box (with a 5" woofer) and had a DAT tape played at

reasonable level through it (without his knowledge, of course). I then

asked him a music related question about what he was listening to... He

answered that anything through XXX cabs always sound great. This

example shows that the brain is messing the equation big time.

 

IMHO, getz76 nailed it pretty much when he pointed out that overdriven

tube and solid state equipment sound different. A slightly overdriven

tube circuit will add (nice) color to the overall sound and will be

registered as louder by the brain. Solid state will not process the same

overdrive the same way, it will sound bad and you will back off the

volume (unless a tube emulator is used - and it's in the preamp

section).

 

First thing, you don't want to overdrive your power amp. So if you want

that sound, get a tube preamp (or a good emulator), and use your power

amp and cab within spec. On the power amp/speaker side, so many factors

could influence the end result, starting with the fact that the output

stage of an SS amp is almost always resistive: the lower the load is,

the higher the current (and power) is going to be, and abuse =

destruction. On the other hand, tube amp must have correct impedance

matching to the load to get rated performances: higher OR lower is bad,

but far more forgiving.

 

Oh, and one electric watt is one electric watt, it's the product of: the

voltage provided by the amp and measured across the load, - and - the

current drawn by the load from the amp. This is not to confuse with the

effective sound pressure you are going to hear.

 

Anything else which could make one setup sound louder than another one

very * equivalent in capability and efficiency * would depend on the

way the audio program is presented to the setup, and the brain messing

with the result.

 

Bob

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